Look at the size of your fish tank. 3, 5 and 7 are all good numbers. Haven't you ever heard of raising fish without double? Tropical fish with white color are generally called feng shui fish, arowana, lucky and so on ~ ~ Remember, miscellaneous fish are not counted in the miles (scavengers).

If the conditions are good, you can raise a better arowana alone, a little bigger ~ ~ but a little monotonous, depending on your personal preference ~